Hacks By Camwi

For those of you who don't know, Obsidian Conflict is one of a couple big coop mods on half life 2. This is about the patch however, not the mod, wanna learn about the mod? Basically they have new NPCs, new weapons, a customizable HUD and flashlight, as well as support for half life source through half life 2: episode 2.
http://www.obsidianconflict.com/

Big changes:
-Now on the orange box.
-Fixed random crashes. At least I'm pretty sure they're all fixed. Go yell at the beta testers if you do find any.
-Custom model support.
-Ironsights. They serve no real purpose, just a fun little thing you can do.
-Alyxgun a usable weapon. (thanks to HL2:CTF for letting the team use that model)
-Merchant now is fully operational. (RE4 voice not included)
-Scripted weapons, fully usable with both normal people and NPCs.
-Lag compensation now makes firing accurately possible in the mist of combat.
-The ichthyosaur works now as a real enemy.
-Scripts for the entire half life 2 campaign, and most of the episodes. I think they also got half life source scripts working but not sure on that one.
-An inventory for small props (like keys)
-Boosting now works.
-A lot of new maps.

"After one and a half years, we have finally finished Obsidian Conflict version 1.3. There are lot of reasons for the many delays (real life, bugs popping out of nowhere, and the change to the Orange Box engine, which brought the mod back to a very broken stage and stifled our passion), but in the end we finally made it and we are proud to present you version 1.3, which is a gigantic step forward from the now-crippled version 1.23.
New features, new maps and the full Half-Life 2 and Episodes story playable in co-op is what you will get with 1.3. So what are you waiting for? Head over to the downloads section and get your copy today!"